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Boiler Basics 101: Burners

The burner is the key equipment component for combustion control systems, providing the heat required for a boiler to convert water into steam. Ideally, a burner should achieve the highest degree of combustion efficiency with the lowest possible excess air. In this month’s edition of Boiler Basics 101, we will discuss the importance of burners and how they fit into the overall picture within the boiler system.

An industrial burner provides a basic function with a simple concept: it mixes fuel and air together to create combustion. Burners can be fired on various types of fuel but the most common utilized are natural gas, oil, propane and coal. In recent years, facilities have moved away from the use of coal to a more efficient and cleaner fuel like natural gas.

Regardless of the type of fuel used, the burner must perform five functions:

  1. Deliver fuel to the combustion chamber
  2. Deliver air to the combustion chamber
  3. Mix the fuel and air
  4. Ignite and burn the mixture
  5. Remove the products of combustion

Complete combustion occurs when all combustible elements and compounds of the fuel are entirely oxidized. However, with complete combustion comes harmful byproducts of combustion, including NOx and CO.

The amount of NOx and CO generated depends greatly on the burner design as well as the fuel fired. Burners with uncontrolled NOx may produce 60 ppm or more. Low NOx burners are the current standard and typically produce NOx of 30 ppm. Ultra-low NOx designs have been developed but are limited to firing on natural gas or propane. These types of burners will reduce NOx emissions to as low as 5 ppm to meet strict environmental requirements that are now common in certain parts of the country. If further NOx reduction is required, Nationwide Boiler’s CataStak™ SCR system can be utilized in conjunction with a low NOx burner.

The right burner design, along with proper combustion controls, will maximize the efficiencies of your boiler system. And as a representative of Webster Combustion, Nationwide Boiler and Pacific Combustion Engineering can help in the proper selection of your new or retrofit burner.

Be sure to check out our next Boiler Basics 101 blog to continue learning about various boiler-related topics.

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Combustion Air Fan & Efficiency

In order for your boiler to operate at peak efficiency, it is important that the correct balance of fuel and combustion air is achieved. Air and fuel ratios are controlled through linkages, fans, dampers and the increase or decrease of gas pressure. Gas pressure is controlled through a pressure regulator and a fan controls the volume of combustion air.
If there are any problems with the fan, more energy may be introduced into the system, causing decreased efficiency. To help ensure that your equipment is running at its peak performance, please review the common fan problems below.

Fan Capacity/Pressure is Below Rating:

  1. Dampers or variable inlet vanes are not adjusted properly

  2. Fan inlet or outlet conditions are impaired

  3. Multiple air leaks within the system

  4. Damage sustained to the blower wheel

  5. Direction of rotation is incorrect


Fan Vibration:

  1. Worn bearings

  2. Unstable foundation

  3. Foreign material in the fan causing an imbalance

  4. Misalignment of bearings, couplings, wheel or v-belt drive

  5. Damaged wheel or motor

  6. Bent shaft

  7. Worn coupling

  8. Loose dampers or variable inlet vanes

  9. Speed too high or incorrect fan rotation

  10. Vibration to fan transmitted from another source

  11. Uneven blade wear

  12. Loose or broken bolts or set screws


Overheated Bearings:

  1. Improper lubrication

  2. Poor alignment

  3. Damaged wheel or driver

  4. Bent shaft

  5. Abnormal end thrust

  6. Dirt in bearings

  7. Improper belt tension


Overload on Driver:

  1. Speed too high

  2. Direction of rotation is incorrect

  3. Bent shaft

  4. Poor alignment

  5. Improper lubrication

  6. Wheel wedging or binding on fan housing

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Recent comment in this post
Guest — IndustrialBlowersandFans
An exhaustive checklist. Bookmarked!
Thursday, 29 October 2009 08:07
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